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Breaking Barriers

The human body has many natural barriers intended to prevent microorganisms, diseases, and toxins from making it into the body. The mucus membranes of the respiratory, gastrointestinal, and female reproductive tracts, for instance, trap bacteria, viruses, and other particles and flush them out of the body. Then there is the formidable blood-brain barrier, which allows the important give-and-take of key signaling molecules, nutrients, and waste products between blood and brain, but prevents the efficient penetration of large molecules, bacteria, and viruses. Unfortunately, sometimes these barriers prove too effective, especially where medicine is concerned. While they protect the body, they also prevent drugs and therapeutic gene-bearing particles from reaching their intended targets.

In recent years, a new field that blends the can-do pragmatism of engineering and the therapeutic magic of medicine has sought to tackle these challenges by packaging existing medicines in new ways to deliver drugs to places in the body that were once out of reach. It works at the smallest scales of matter where a hundred nanometers—a distance smaller than the wavelength of light—can mean the difference between a drug that reaches a malignant tumor and one that does not. The field is known as nanomedicine.

“We’re not making new drugs. We’re making existing drugs better by engineering ways to package them differently at the nanoscale—molecule by molecule—to help them transcend the body’s natural barriers,” says Justin Hanes, MD, who directs the Johns Hopkins Center for Nanomedicine. Hanes is the Lewis J. Ort Professor of Ophthalmology at the Wilmer Eye Institute and a chemical engineer by training. Researchers from across Hopkins Medicine are using nanomedicine in fields ranging from oncology and ophthalmology to sexually transmitted diseases.